BoilerFaultCodesYour boiler has shut down because the water inside is heating up much faster than it can be moved around the system, usually due to a blockage or a pump issue.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Safety switch-off – temperature rise too fast
What causes this fault?
This fault occurs when the heat exchanger gets too hot because the water isn't flowing away from it quickly enough. The most common reasons are a failing pump that can't push the water through or a build-up of sludge and debris blocking the internal pipework. In some cases, it can also be caused by air trapped in the system or a faulty sensor misreading the temperature.
This issue often comes to light when turning the heating back on for autumn, as pump components can seize up after being idle over the summer.
DIY fix possible
Ensure all radiator valves (TRVs) are fully openCheck that the boiler pressure is between 1.0 and 1.5 barPress the reset button once to see if the fault clears
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like F.24 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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